Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $188.50   8.741%   $204.9768   $204.98   $205.00   $205.00  
  Purchase #2 $56.27   7.563%   $60.5257   $60.53   $60.55   $60.50  
  Purchase #3 $8.61   13.177%   $9.7445   $9.74   $9.75   $9.70  
  Purchase #4 $214.94   8.658%   $233.5495   $233.55   $233.55   $233.50  
  Purchase #5 $208.93   7.841%   $225.3122   $225.31   $225.30   $225.30  
  Purchase #6 $174.69   12.327%   $196.224   $196.22   $196.20   $196.20  
  Purchase #7 $78.81   6.767%   $84.1431   $84.14   $84.15   $84.10  
  7 purchase totals = $930.75       $1,014.4758   $1,014.47   $1,014.50   $1,014.30